Touch sensing technology capable of providing a natural interface between an electronic system and user has found widespread applications in a variety of fields, for example, in mobile phones, personal digital assistants (PDAs), automatic teller machines (ATMs), game machines, medical devices, liquid crystal display (LCD) devices, light emitting diode (LED) devices, plasma display panel (PDP) devices, computing devices, and the like, where a user may input desired information and/or operate the electronic system through a touch sensing device associated with the electronic system. A touch sensing device typically includes a controller, a sensing circuit having a plurality of touch sensors and a network of control lines electrically connecting the plurality of touch sensors to the controller, and a touch screen associated with the plurality of touch sensors.
There are at least two types of touch sensors available for detection of a touch location. One is a resistive touch sensor that includes two layers of transparent conductive material, such as a transparent conductive oxide, separated by a gap. When touched with sufficient force, one of the conductive layers flexes to make contact with the other conductive layer. The location of the contact point is detectable by a controller that senses the change in resistance at the contact point. In response, the controller performs a function, if any, associated with the contact point. The other is a capacitive touch sensor that typically includes a single conductive layer for touch detection. A finger touch to the sensor provides a capacitively coupled path from the conductive layer through the body to earth ground. The location of the contact point is detectable by a controller that measures a capacitance change in a capacitively coupled electrical signal at the touch location. Accordingly, the controller performs a function, if any, associated with the touch location.
Conventional capacitive touch panels utilize diamond-type electrodes, as shown in FIG. 1a, and triangle-type electrodes, as shown in FIG. 1b, as sensing units. For a triangle-type touch panel, it utilizes the variation of the capacity generated between two up-and-down cross triangles and a figure to detect the coordinates of the touch location. However, its linearity is not very accurate. The triangle-type touch panel is rarely used now.
For the diamond-type touch panel, a plurality of first touch electrodes 110 and a plurality of second touch electrodes 120 are spatially arranged to form a sensing array. The width of the diamond electrode defines a pitch of the sensing units. For a large sized panel, either the pitch of the sensing units needs being enlarged, or the number of the sensing units needs being increased. However, the pitch cannot be enlarged indefinitely, since the limitation of the figure size. If the pitch is too large, the finger cannot simultaneously touch two or more sensing units to induce an effective capacity, thereby not being able precisely to detect the coordinates of the touch location by utilizing the variation of the capacity of the two or more sensing units. Therefore, the pitch of the sensing units is generally of about 4-6 mm. On the other hand, since the channels supported by an IC are also limited, the number of the sensing units cannot be increased unlimitedly. Therefore, the diamond-type capacitive touch panel is usually designed to have a size of about 12 inches or less. If the size is larger than 12 inches, the touch detection has a poor linearity, and touch panel can not be utilized for precisely detecting the coordinates.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.